In this tutorial you will learn how to use AIP to register two images and to blink the images. The registration is done at the sub-pixel level. When two images are blinked, they are alternately displayed in rapid succession. The rate at which the display is alternated can be controled by the user. Blinking is useful for searching for differences between the two images. In particular, anything that moves during the time interval between the two images will appear to hop or jump between two positions when the images are blinked. Anything that changes in brightness during the time interval between the two images will appear to blink or flicker when the images are blinked. Blinking is a standard procedure that can be used to detect or to discover...
Periodic error in the telescope drive, and minor misadjustment of the telescope tracking rate will normally require registration even for a second image taken after several hours or even after several minutes. Differences in exposure time or changing conditions will cause images of all objects in the frame to blink.
Pick out two CCD images that are of the same field and follow along with the steps outlined below. While using the registration and blinking tools it is advisable to have the Auto-Stretch feature selected on the Display Control window.
Step 1: Load the Images
Load the two images you wish to register and blink.
Step 2: Select the Register Images Tool
Find the tool by proceeding as follows...
Multi-Image | Register Images...
The Image Registration tool will appear.
Step 3: Select the Reference and Subject Images
You should see two image frames labelled Reference Image and Subject Image. Use the drop-down list on the Reference Image to select the image you will use as your standard (reference). In the drop-down list on the Subject Image select the image you will use as your target (subject) image.
Step 4: Select the Allignment Stars
Each image is displayed in its own window, with the upper-left corner visible. You can scroll across each of the images. Your goal is to select the same stars in each image. Find a clean star image in the upper-left corner of the Reference Image. Click on the star and then click the Star 1 button for that image. Now find the same star in the Subject Image and click on the star. Then click on the Star 1 button for that image.
Use the sliders on each image display to move to the lower-right portion of the images. Find another suitable star in this portion of the image and use the Star 2 button for each image.
The best image registration will result from star images that are widely separated in the frame. When the Subject Image is alligned, it is translated, rotated, and scaled to match the Reference Image. Selecting star images that are too close together in the frame will produce registrations of reduced accuracy.
Step 5: Perform the Allignment
Once the allignment stars have been selected in both images click the Apply button. This will create a new image that is the Subject image transformed to the coordinate system of the Reference Image. This is your transformed, registered image
Step 6: Select the Blink Images Tool
Find the Blink tool as follows...
Multi-Image | Blink
The Blink Images Tool will appear.
Step 7: Select the Images to Blink
The Blink Images Tool contains two drop-down lists. For the top list, select your standard (reference) image. For the lower list select your registered image.
Step 8: Blink the Images
Click Manual several times. You will see anything that has changed either hop back and forth, or "blink." bright and faint. You may also see any cosmic ray hits on either of the images. If you have selected two images for which nothing has changed (not a good idea for this tutorial) you may see no differences.
Step 9: Auto-Blink
Click Auto and the images will blink continuously. You can control the rate by using the Blink Interval slider. You can stop this process by clicking the Stop button.
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